Duel Monitors

I've just read a previous thread about having two monitors running on one pc. It said that all you need is a video card running in a pci slot and one running in an agp slot. That seems simple enough, but is that all there is two it? Will any changes need to be made in the bios? How does one keyboard and one mouse control two screens, is it as simple as pressing a 'hotkey' to alter which screen you are controlling? Do you need to be using a certain type of video card? Can someone please provide me with an idiots guide on how to do this.I'm running XP Pro and a 3D Prophet 4000XT Pci video card.